

• " .' iNIll \ 



;.niw p] a ckoned to th< embryonal stage, but that I cannot aj 



w ith th th( embryo, however, in the different Pycnogonida , breaks the egg shell some- 



tiui, .1 shorter, sometimes after a longer development, nay, sometimes not even, until all the 



limb mbulator) legs included, have been developed, it will be underst 1 thai Korschell and 



Heider, Lehrb. Entwick wirbell. Thier. [890, in their large, well known text 1 k can sa) ol the 



inida that only » 1 i <-- meisten Pantopoden entwickeln sich mittelsl Metamorphose . Lc p. 662, 

 were anj important difference between the different Pycnogonida; Dohrn, Pantop. Golf, 

 even says i.e. p. 77: Pallene hal die ganze Larvenentwickelung vollkommen unter- 

 driiekt, das junge Thier, welches die Eischale verlasst, besitzt bereits alle definitive Extremitaten, 

 wenn audi aoch nicht in definitiver Gestalt < >n the following page we find: Wenn der Embryo 

 seine Reife erreicht hat, gleicht er in vielen Beziehungen der Larve von Phoxichilidium , welche den 

 Hydroidpolypen verlasst . In mj opinion the peculiarity in Pallene emaciata, the species mentioned 

 bj Dohrn, is "illy to be found in the fact that the larva completes its development in the egg, in- 



I g shell; and that this fact is not t<> be underst 1 as something general in the genus, but 



onl) as a peculiarity in this species among known forms I infer from the fact that in another Pallene- 

 ies, Pallene haslata, 1 have found all larvae free with only three pairs of developed ambulatory 

 », pi. 1, Kg 18 in. In the nearly related genus Pseudopallene I have even found the larva free in 

 its first stage with the two foremost pairs of ambulatory legs not yet quite developed, pi. I, fig.8. In 

 the following I shall enter into further details as to this fact. Also in other genera, for inst in .Vvw- 

 phon, it may he found in the different species that the larvae leave the egg shell sooner or later, with- 

 out an) other difference in the course of development. It is quite another thing that a good bound- 

 really exists, but it can as usual he placed at the origin of the first larval form, here according- 

 ly it i^ to he applied to the form that has been called Protonymphon (Hoekj or the Pantopod- 

 larva 1 Dohrn). 



Alreadj in the introduction to this section on the larval development, I spoke of the usual 

 misconception with regard to the duration of the embryonal life, and gave a quotation frem the text- 

 hook b) Korschelt and Heider. I have here tried by demonstration on my figures to maintain 

 more in detail that all Pycnogonida pass through the same scries of larval stages, whether the larva 

 Protonymphon frees itself at once, or remains in the egg till all the ambulator) legs ar< developed, 

 even if it has not attained its full length, segmentation, or all its appendages. 



When the yolk-division is equal the whole blastoderm, onl) excepting the 

 middle and hinder parts of the dorsal side, participates in the form a t ion of the em- 

 bryonal limbs and the proboscis. The embryo is free at once, is considered to be a 

 full) devi larva in the first stage, and is called Protonymphon (Hoek) or Pan- 



larva kat' exochen 1 Dohrn, Morgan). 



It is the enormous, overriding development of the embryonal limbs and the proboscis that is 



this larval form, and this feature is found spread through the whole system 



nida, and has been known and described in different genera, as Phoxichilidium, Pycno- 



iltts, Ammothca (Achelia), Ascorhynchus, and Tanystylum. It is also this larval form 



which I inall) played the greatest | to tin- question of the systematic position of the 



